Plasma processing method and plasma processing apparatus

Abstract

A plasma processing method includes applying a pulse wave of high frequency electric power for plasma generation and a pulse wave of high frequency electric power for bias whose frequency is lower than that of the high frequency electric power for plasma generation on the mounting table; and controlling the pulse wave of the high frequency electric power for plasma generation and the pulse wave of the high frequency electric power for bias such that a predetermined phase difference is generated between the pulse wave of the high frequency electric power for plasma generation and the pulse wave of the high frequency electric power for bias, and a duty ratio of the high frequency electric power for plasma generation becomes greater than or equal to a duty ratio of the high frequency electric power for bias.

What is claimed is: 
     
       1. A plasma processing method using a plasma processing apparatus including
 a process chamber, 
 a mounting table provided in the process chamber, and 
 an electrode provided to face the mounting table, of plasma processing a substrate on the mounting table, the method comprising: 
 applying a pulse wave of high frequency electric power for plasma generation and a pulse wave of high frequency electric power for bias whose frequency is lower than that of the high frequency electric power for plasma generation on the mounting table; 
 controlling the pulse wave of the high frequency electric power for plasma generation and the pulse wave of the high frequency electric power for bias such that a predetermined phase difference is generated between the pulse wave of the high frequency electric power for plasma generation and the pulse wave of the high frequency electric power for bias, and a duty ratio of the high frequency electric power for plasma generation becomes greater than or equal to a duty ratio of the high frequency electric power for bias; and 
 etching the substrate on the mounting table under a condition controlled in the controlling, 
 wherein in the controlling, the pulse wave of the high frequency electric power for plasma generation and the pulse wave of the high frequency electric power for bias are controlled to generate the predetermined phase difference capable of suppressing generation of a standing wave of high harmonics waves generated due to the superimposition of the pulse waves, 
 wherein in the controlling, the duty ratio of the high frequency electric power for plasma generation is set greater than the duty ratio of the high frequency electric power for bias to a degree capable of selectively increasing an etching rate at a middle portion of the substrate between a center portion and an edge portion of the substrate. 
 
     
     
       2. The plasma processing method according to  claim 1 , further comprising:
 providing gas containing hydrogen bromide (HBr) gas, nitrogen trifluoride (NF 3 ) gas and oxygen (O 2 ) gas, or gas containing hydrogen bromide gas, CF based gas and oxygen gas in the process chamber, and etching a polysilicon film formed on the substrate using a silicon oxide film formed on the polysilicon film as a mask. 
 
     
     
       3. The plasma processing method according to  claim 1 ,
 wherein frequency of the high frequency electric power for plasma generation is within a range of 100 MHz to 150 MHz and frequency of the high frequency electric power for bias is within range of 400 kHz to 13.56 MHz. 
 
     
     
       4. The plasma processing method according to  claim 1 ,
 wherein in the controlling, the duty ratio of the high frequency electric power for plasma generation is set greater than or equal to two times of the duty ratio of the high frequency electric power for bias.